The aim of this project is to evaluate the influence of a number of hormones, including dexamethasone, thyroxine, cyclic AMP, insulin and estrogen on the biochemical and morphologic development of fetal rat lung in organ culture and to investigate the role of the mesenchymal tissue in regulating lung epithelial cell development. Organotypic cultures of fetal rat lung will also be evaluated and studied. Specifically the role of glycogen in fetal lung phospholipid synthesis will be studied and the influences of hormones on glycogen and phospholipid metabolism, includingthe activities of enzymes involved in these processes will be examined. The importance of the mesenchyme in mediating hormonal influences on fetal lung epithelial development will be determined in a separate series of organ culture studies.